TL;DR

Do aluminium PCB heatbeds suffer from hotspots as much as standard PCB heatbeds, or is the presence of hot spots smoothed over by the fact that the PCB "substrate" is aluminium, and so its thermal conductivity helps spread the heat more evenly?

Or, conversely, could the effect of the hotspots be magnified, and actually made worse?

Which has fewer hotspots, MK2A, MK2B, or MK3? (I'm not sure if this should be a separate question)

I would have also asked whether aluminium PCB heatbeds are worth the additional cost, over standard PCB heatbeds, but for the slightly less common dimensions of 200 mm x 300 mm, the costs, of an aluminium PCB heat bed, are roughly the same as standard PCB.

Some thermal imaging pictures, comparing standard PCBs with aluminium PCBs, would be appreciated.

As stated in the former link, on the section on Metal print beds, PCB based heatbeds can suffer from hotspots, and that is why, apparently, it is sometimes preferrable to use a subsequent aluminium build/print bed on top of that, en lieu of glass plate, in order to even out the hotspots, as the aluminium's greater thermal conductivity helps smooth out the hotspots, by distributing the heat more efficiently than a glass plate can. However, it doesn't describe the heating effect of just a single aluminium PCB heatbed.

The section, in the latter link, on Aluminium heatbeds, where the heating circuit is printed directly onto the aluminium, rather than a standard PCB (on a non-conductive substrate), makes mention that the print can be made directly on to the aluminium, without the need of an additional glass plate, resulting in a lighter print plate, and hence faster print speed. However, yet again, it is not particularly clear, or explicit, when it comes to heat distribution.